TPU polymers are typically made by reacting (1) a hydroxyl terminated polyether or hydroxyl terminated polyester, (2) a chain extender, and (3) an isocyanate compound. Various types of compounds for each of the three reactants are disclosed in the literature. The TPU polymers made from these three reactants find use in various fields where products are made by melt processing the TPU and forming it into various shapes to produce desired articles by processes such as extrusion and molding.
TPUs are segmented polymers having soft segments and hard segments. This feature accounts for their excellent elastic properties. The soft segments are derived from the hydroxyl terminated polyether or polyester and the hard segments are derived from the isocyanate and the chain extender. The chain extender is typically one of a variety of glycols, such as 1,4-butane glycol.
U.S. Pat. No. 5,959,059 discloses a TPU made from a hydroxyl terminated polyether, a glycol chain extender, and a diisocyanate. This TPU is described as being useful for making fibers, golf ball cores, recreational wheels, and other uses.
Blooming is a problem that is frequently observed in articles made with thermoplastic polyurethanes. Blooming is something also referred to as “surface haze” or “surface fogging.” Blooming is undesirable because it can destroy the aesthetic surface characteristics of articles made with polymers that bloom. It is particularly undesirable for bloom to occur in articles where clarity is desired. Bloom is also undesirable because it can reduce the ability of an article made with the blooming polymer to be securely bound to other article with adhesives. Blooming has long been recognized as serious problem in some applications and an effective means for alleviating it as been sought for years.
U.S. Pat. No. 5,491,211 discloses a thermoplastic polyurethane composition that is reported to be bloom-free. This objective is reported to be accomplished by including a monofunctional compound that is reactive with isocyanates in the thermoplastic polyurethane composition. U.S. Pat. No. 5,491,211 specifically discloses the use of monofunctional alcohols that contain at least 14 carbon atoms, such as 1-tetradecanol, 1-octadecanol, or 1-docosanol, for the purpose of controlling bloom.